Have you read the first forest griffin book - 50 zen principles of hand to face combat? he talks about street fighting and suggests (through several years of trial and error of course) that you never take the fight to the ground if possible, especially ending up on your back, pulling guard or whatever. so much shit on the ground that can damage you, no telling when back up for your opponent might arrive. After a good few brawls myself and being a fan of BJJ I am also not sure you would even want to find yourself on the ground.
maybe freestyle wrestling as a way to establish top position? big double leg to side control and a bit of GNP JBJ style? would definately work for me!
as Bowral said. good to see a thread like this and see so many combat sports enthusiasts around the place.